﻿Shader "Custom/RampTexture"
{
   Properties{
        _Color("Color",Color) = (1,1,1,1)
        _RampTex ("RampTex" , 2D) = "white" {}
        _Specular ("Specular" , Color) = (1,1,1,1)
        _Gloss("Gloss", Range(2,200)) = 20
    }
    
    SubShader{
    
        Pass{
            Tags{"LightMode" = "ForwardBase"}
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "Lighting.cginc"
            
            fixed4 _Color;
            fixed4 _Specular;
            sampler2D _RampTex;
            float _Gloss;
            float4 _RampTex_ST;
            
            struct a2v{
                float4 vertex : POSITION;
                float3 normal : NORMAL;
                float4 texcoord : TEXCOORD0;
            };
            
            struct v2f{
                float4 pos : SV_POSITION;
                float3 worldNormal : TEXCOORD0;
                float3 worldPos : TEXCOORD1;
                float2 uv : TEXCOORD2; 
            };
            
            v2f vert (a2v v){
               v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
                o.worldNormal = UnityObjectToWorldNormal(v.normal);
                o.uv = TRANSFORM_TEX(v.texcoord, _RampTex);
                return o;
            };
            
            fixed4 frag (v2f f) : SV_Target {
                fixed3 worldNormal = normalize( f.worldNormal );
                fixed3 worldLightDir = normalize( UnityWorldSpaceLightDir(f.worldPos ) );
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz;
                fixed halfLambert = 0.5 * dot ( worldNormal, worldLightDir ) + 0.5;
                //这里使用半兰伯特计算后的结果，去取样渐变图uv颜色
                fixed3 diffuseColor = tex2D( _RampTex,  fixed2( halfLambert, halfLambert)).rgb * _Color.rgb;
                fixed3 diffuse = _LightColor0.rgb * diffuseColor;
                fixed3 viewDir = normalize ( UnityWorldSpaceViewDir (f.worldPos) );
                fixed3 halfDir = normalize( worldLightDir + viewDir );
                fixed3 specular = _LightColor0 * _Specular.rgb * pow ( saturate( dot ( worldNormal, halfDir )), _Gloss );
                return fixed4 (  diffuse + ambient ,1);
            };
            
            
            
            ENDCG
            
        }
    
    }
    
    
    FallBack "Diffuse"  //后备方案
}
